One way for improving brightness of a backlight source is to replace a white reflector film with an enhanced specular reflector (ESR) film. A reflectivity of a normal ESR film is about 15% higher than that of the white reflector film. Since a surface of the ESR film is a mirror surface, masking properties of the ESR film for white filaments and white dot particles is about 5% lower than that of the white reflector film. Thus, the ESR film can improve brightness but the yield of the backlight source decreases.
In addition, small sized LEDs may be adopted to increase the number of LEDs arranged in a light bar. However, as sizes of the LEDs decrease, the price of the LEDs will increase more. Meanwhile, as the size of each LED decreases, a junction temperature of each LED will rise, and then the risk of notebook overheating is increased as there are many LEDs in the whole light bar.